The Virginia General Assembly is expected to vote on a two-year state spending plan Tuesday, a move critical for several Northern Virginia transportation projects.

Funding for Phase 2 of the Dulles Corridor Metrorail Project within the $85 billion budget has been a key storyline in the 2012 session, with Gov. Robert F. McDonnell (R) and Virginia Transportation Secretary Sean Connaughton playing starring roles.

Last week, McDonnell announced that moving forward with an additional $300 million for Phase 2 could jeopardize the progress on 40 transportation projects across the state, including two high-priority items in Loudoun County — the interchange at Route 659 and extending Battlefield Parkway.

At the opening of the 2012 General Assembly session, McDonnell pledged $150 million in state funding for Phase 2. Saying that amount was shortchanging a transportation project of local, state and federal significance, state Sen. Mark Herring (D-Dist. 33) joined a coalition of Democrats pushing for more state funding.

In March, it appeared those efforts paid off. After Senate Democrats refused to adopt a House of Delegates budget that didn’t fund Metrorail, the full Senate approved a spending plan that included the additional $300 million for rail, as well as $65 million for the cost of competing education funds in Northern Virginia.

At that point, it seemed the equally-divided Senate was poised to see a budget sufficient for transportation and education, Herring said.

Less than two weeks later, however, 12 negotiators from both the House and Senate reached a budget deal that failed to include any rail funds beyond the original $150 million. Any state dollars beyond that amount would require a hold to be put on other state transportation projects.

Herring has blamed McDonnell’s administration for flip-flopping on the $300 million for rail.

“All this administration is doing now is showing their content with tolling people to death,” Herring said.

Without more state funding for Phase 2, tolls in Northern Virginia might double within a year to help pay for the Metrorail project. Tolls in the region have been estimated to cost the average commuter more than $2,200 per year. In Hampton Roads, commuters are anticipated to shell more than $1,000 per year on the downtown and midtown tunnels, according to state Sen. Richard Saslaw (D-Dist. 35)

“Tolls are taxes on the people who can least afford them,” Saslaw said.